Scientists at The Rockefeller University discovered some people who tend to
stay awake for long hours at night have a variant of CRY1gene causing the
slowing down of their biological clock. The result of their study is
published in Cell.

"Compared to other mutations that have been linked to sleep disorders in
just single families worldwide, this is a fairly impactful genetic change,"
said Michael W. Young, lead author and head of Rockefeller's Laboratory of
Genetics. According to the study, the mutation may occur in as many as one
in 75 people in some populations.

The researchers required the subjects to stay in a laboratory apartment for
two weeks. They were isolated from all cues to the time of day and were
allowed to eat and sleep whenever they needed. Samples of skin cells were
also collected from them. Most of the subjects showed a 24-hour sleep-wake
cycle. However, those with delayed sleep phase disorder (DSPD) had longer
cycles. Changes in body temperature and hormones linked to the biological
clock were also delayed. Melatonin, a hormone that helps regulate sleep,
usually increase around 9 or 10 in the evening for most people, but those
with DSPD get higher levels of melatonin at around 2 or 3 in the morning.
The DNA samples of the subjects were also studied and the researchers found
that a mutation in CRY1 is common among DSPD patients.

[newswire.rockefeller.edu]
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